JP2015102651A - Two-component developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-component developer that includes a carrier that prevents the fusion of resin fine particles detached from the surface of toner base particles to maintain good charge stability.SOLUTION: There is provided a two-component developer including a capsule toner in which resin fine particles are coated on the surface of a toner base particle and a coat carrier in which a carrier coating layer is formed on the surface of a carrier core material particle, where the carrier coating layer has fine projections formed thereon.

Description

  The present invention relates to a two-component developer using a capsule toner.

  An image forming apparatus that forms an image using an electrophotographic method includes a photosensitive member, a charging unit that charges the surface of the photosensitive member, an exposure unit that forms an electrostatic latent image on the surface of the photosensitive member, and a toner image formed from the electrostatic latent image. A developing unit for transferring the toner image onto the recording medium, a fixing unit for fixing the toner image on the recording medium, and a cleaning unit for cleaning the surface of the photoreceptor.

  In such an image forming apparatus, a one-component developer containing toner or a two-component developer containing toner and a carrier is used as a developer for developing an electrostatic latent image and forming a toner image. Further, with the trend of colorization in recent years, toners have been fixed at low temperature, and toner components having a low temperature softening tendency tend to be used.

  Therefore, as a toner having good fluidity, transferability, etc., uniform charging performance, excellent anti-offset property, and various other functions, a capsule toner in which the surface of toner base particles is coated with a resin layer is used. Proposed.

  For example, in Patent Document 1 and Patent Document 2, the toner base particles and the resin fine particles are stirred and mixed by a mixer, the resin fine particles are attached to the surface of the toner base particles, and then a mechanical impact force is applied. A method for producing a capsule toner by coating resin fine particles on the surface of toner base particles is disclosed.

Japanese Patent Laid-Open No. 5-281787 JP 2001-324831 A

  However, when the capsule toner described in Patent Document 1 or Patent Document 2 is used as a two-component developer, there is a problem that the charging performance of the carrier decreases with the use time and the image quality deteriorates. As shown in FIG. 2, when the capsule toner 50 is stirred in the developing device and receives a shearing force, the resin fine particles 52 that have not been sufficiently coated are detached from the surface of the toner mother particles 51, and between the carriers 60. It is considered that the resin fine particles 52 rubbed and melted by frictional heat are fused to the surface of the carrier 60.

  In view of the above problems, an object of the present invention is to provide a two-component developer having a carrier in which resin fine particles detached from the surface of toner base particles are hardly fused and having excellent charging stability.

  The two-component developer of the present invention is a two-component developer comprising a capsule toner in which resin fine particles are coated on the surface of toner base particles, and a coated carrier in which a carrier coating layer is formed on the surface of carrier core particles. The carrier coating layer is characterized in that fine protrusions are formed.

  Further, the minute protrusions are formed by spherical fine particles.

  The spherical fine particles are characterized in that the average particle size is 2 to 5 times the average particle size of the resin fine particles.

  The spherical fine particles are polytetrafluoroethylene particles.

  The carrier coating layer includes a silicone resin.

  According to the two-component developer of the present invention, the resin fine particles detached from the toner coating layer can be prevented from being fused to the carrier, and excellent charging stability can be maintained.

FIG. 2 is a schematic diagram illustrating a schematic configuration of a two-component developer according to an embodiment of the present invention. It is a schematic diagram which shows schematic structure of the conventional two-component developer.

(Two-component developer)
FIG. 1 is a schematic diagram showing a schematic configuration of a two-component developer 1 according to an embodiment of the present invention. The two-component developer 1 of the present invention includes a capsule toner 10 in which resin fine particles 12a are coated on the surface of toner base particles 11, and a coated carrier 20 in which a carrier coating layer 22 is formed on the surface of carrier core material particles 21. And a fine protrusion 23 is formed on the carrier coating layer 22.

  According to the two-component developer 1 of the present invention, since the fine protrusions 23 are formed on the surface of the coat carrier 20, when the two-component developer 1 is agitated in the developing device, the two coat carriers 20 that are close to each other. Meshing with each other's microprotrusions 23 and rotating, thereby functioning to discharge the resin fine particles 12a interposed between the coat carriers to the outside and preventing the resin fine particles 12a from being fused to the surface of the coat carrier 20. Can do. Hereinafter, the capsule toner 10 and the coat carrier 20 included in the two-component developer 1 according to the embodiment of the present invention will be described.

≪Capsule toner≫
As shown in FIG. 1, the capsule toner 10 includes toner base particles 11 and a toner coating layer 12 formed on the surface of the toner base particles 11 and a toner coating layer 12 formed by coating resin fine particles 12a.

<Toner base particles>
As the toner base particles 11, particles having a volume average particle size of 5 to 8 μm including a binder resin, a colorant, a charge control agent, a release agent and the like are generally used.

(Binder resin)
As the binder resin, a polyester resin, a styrene acrylic resin, or the like can be used. The glass transition point of the binder resin is preferably 40 ° C. or higher and 60 ° C. or lower, and the softening temperature of the binder resin is preferably 80 ° C. or higher and 140 ° C. or lower.

(Coloring agent)
As the colorant, organic dyes and organic pigments commonly used in the toner field can be used, and 2 to 10 parts by weight of the colorant is added to 100 parts by weight of the binder resin.

  Examples of the black colorant include carbon black and magnetite.

  Examples of the yellow colorant include C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 138, and the like.

  Examples of the magenta colorant include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of cyan colorants include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. And CI Pigment Blue 60.

(Charge control agent)
As the charge control agent, a charge control agent for positive charge control and negative charge control used in general toners can be used, and usually 0.5 to 3% by weight with respect to 100 parts by weight of the binder resin. Added in proportions. Examples of the charge control agent for controlling positive charges include nigrosine dyes and quaternary ammonium salts. Examples of the charge control agent for controlling negative charges include azo complex dyes, metal complexes and metal salts of salicylic acid and its derivatives. And boron compounds.

(Release agent)
As the release agent, wax used in general toners can be used, and usually 0.5 to 10 parts by weight of the release agent is added to 100 parts by weight of the binder resin. Examples of the wax include paraffin wax, microcrystalline wax, Fischer-Tropsch wax, polyethylene wax, polypropylene wax, and carnauba wax.

<Toner coating layer>
As shown in FIG. 1, the toner coating layer 12 is formed by coating resin fine particles 12 a on the surface of the toner base particles 11, and an effect of preventing toner aggregation is obtained. Since the surface of the toner base particles 11 is required to be coated with one or more layers of resin fine particles, the mixing ratio of the toner base particles 11 and the resin fine particles 12a is 100 parts by weight of the toner base particles 11. 2 to 20 parts by weight of resin fine particles 12a are mixed.

(Resin fine particles)
As the resin fine particles 12a for forming the toner coating layer 12, for example, a polyester resin, an acrylic resin, a styrene-acrylic copolymer resin, or the like can be used. The glass transition point of the resin fine particles 12a is preferably 55 ° C. or more and 65 ° C. or less, and preferably 5 ° C. to 15 ° C. higher than the glass transition point of the binder resin. The softening temperature of the resin fine particles 12a is preferably 80 ° C. or higher and 140 ° C. or lower. The average particle diameter of the resin fine particles 12a is preferably 0.1 μm or more and 0.3 μm or less.
<Method for producing capsule toner>
A method for manufacturing the capsule toner 10 will be described below. The manufacturing method of the capsule toner 10 includes a toner base particle manufacturing step S1 for manufacturing the toner base particles 11, a resin microparticle manufacturing step S2 for manufacturing the resin microparticles 12a for forming the toner coating layer 12, and the toner base particles 11 And a coating step S3 for forming the toner coating layer 12 with resin fine particles 12a on the surface.

(Toner base particle manufacturing process: S1)
In the toner base particle manufacturing step S <b> 1, toner base particles 11 serving as the core of the capsule toner 10 are prepared. The toner base particles 11 are particles containing a binder resin and a release agent colorant. Examples of methods for producing the toner base particles 11 include a dry method such as a pulverization method, a suspension polymerization method, and an emulsion aggregation method. And wet methods such as a dispersion polymerization method, a dissolution suspension method, and a melt emulsification method. Hereinafter, a method for producing the toner base particles 11 by the pulverization method will be described.

  When the toner base particles 11 are prepared by a pulverization method, a binder resin and a colorant as a toner composition and, if necessary, a release agent and a charge control agent are dry-mixed with a mixer and then melted with a kneader. Knead. The kneaded product obtained by melt kneading is cooled and solidified, and the solidified product is pulverized by a pulverizer. Thereafter, particle size adjustment such as classification is performed as necessary to obtain toner base particles 11.

  As the mixer, for example, a Henschel type mixing device such as a Henschel mixer (trade name, manufactured by Mitsui Mining Co., Ltd.), a super mixer (trade name, manufactured by Kawata Co., Ltd.), a mechano mill (trade name, manufactured by Okada Seiko Co., Ltd.), etc. Ongmill (trade name, manufactured by Hosokawa Micron Corporation), hybridization system (trade name, manufactured by Nara Machinery Co., Ltd.), Cosmo system (trade name, manufactured by Kawasaki Heavy Industries, Ltd.), and the like.

  As a kneading machine, for example, a general kneading machine such as a twin-screw extruder, a three-roller, or a lab blast mill can be used. More specifically, for example, TEM-100B (trade name, manufactured by Toshiba Machine Co., Ltd.), PCM-65 / 87, PCM-30 (all of which are trade names, manufactured by Ikegai Co., Ltd.), etc. Extruder, Needex (trade name, manufactured by Mitsui Mining Co., Ltd.) and other open roll type kneaders. Among these, an open roll type kneader is preferable.

  As the pulverizer, for example, a jet type pulverizer that pulverizes using a supersonic jet stream, and a solidified material in a space formed between a rotor (rotor) and a stator (liner) that rotate at high speed. An impact pulverizer that introduces and pulverizes can be used. As the classifier, for example, a swirling wind classifier (rotary wind classifier) or the like can be used.

(Resin fine particle manufacturing process: S2)
In the resin fine particle manufacturing step S2, dry resin fine particles 12a for forming the toner coating layer 12 that covers the toner base particles 11 are manufactured.

  The resin fine particles 12a are produced by polymerizing monomers using an emulsifying dispersion method, an emulsion polymerization method or a soap-free polymerization method in which a resin raw material is refined in water using a homogenizer while adding a solvent or heat. Then, it can be obtained by drying by a method such as hot air heat receiving drying, conduction heat transfer drying, far infrared drying, microwave drying or the like.

(Coating process: S3)
The covering step S3 is a step of forming the toner covering layer 12 on the surface of the toner base particles 11 to generate a capsule toner, and includes a resin fine particle attaching step S31 and a film forming step S32.

  In the resin fine particle adhesion step S31, the toner base particles 11 obtained in the toner base particle production step S1 and the resin fine particles 12a obtained in the resin fine particle production step S2 are mixed by a mixer, and the surface of the toner base particles 11 is obtained. Resin fine particles 12a are uniformly attached to the whole to obtain resin fine particle-attached toner base particles.

  As the mixer, for example, a Henschel type mixing device such as a Henschel mixer (trade name, manufactured by Mitsui Mining Co., Ltd.), a super mixer (trade name, manufactured by Kawata Co., Ltd.), a mechano mill (trade name, manufactured by Okada Seiko Co., Ltd.), etc. Ongmill (trade name, manufactured by Hosokawa Micron Corporation), hybridization system (trade name, manufactured by Nara Machinery Co., Ltd.), Cosmo system (trade name, manufactured by Kawasaki Heavy Industries, Ltd.), and the like can be used.

  In the film forming step S32, the toner fine particles 12a are fused (filmed) to the toner base particles 11 by applying a mechanical impact force to the resin fine particle-attached toner base particles using a film forming apparatus, and the toner coating layer. 12 is formed. Examples of the membrane forming apparatus include a hybridization system (trade name, manufactured by Nara Machinery Co., Ltd.).

≪Coat carrier≫
The coated carrier 20 of the present invention is provided with carrier core material particles 21 and a carrier coating layer 22 formed on the surface thereof, and fine protrusions 23 are formed on the surface of the coated carrier 20. The volume average particle size of the coat carrier 20 can generally be 25 to 100 μm, but considering the image quality, spherical particles of 20 to 50 μm are preferable, and the magnetization strength (maximum magnetization) is 10 to 10 μm. 60 emu / g is preferred.

<Carrier core particles>
As the carrier core material particles 21, for example, ferrite particles having an average particle diameter of 20 to 90 μm can be used. Examples of the ferrite include zinc-based ferrite, nickel-based ferrite, copper-based ferrite, nickel-zinc-based ferrite, manganese-magnesium-based ferrite, copper-magnesium-based ferrite, manganese-zinc-based ferrite, manganese-copper-zinc-based ferrite, Manganese-magnesium-strontium ferrite and the like can be mentioned.

  The ferrite particles are, for example, mixed with a ferrite raw material such as Fe2O3 or Mg (OH) 2, and this mixed powder is heated in a heating furnace and calcined. After cooling the obtained calcined product, it is pulverized by a vibration mill so as to become particles of about 1 μm, and a dispersant and water are added to the pulverized powder to prepare a slurry. This slurry is obtained by wet pulverizing with a wet ball mill and granulating and drying the resulting suspension with a spray dryer.

<Carrier coating layer>
The carrier coating layer 22 is made of a coating resin and spherical fine particles held thereby, and the fine protrusions 23 are formed by the spherical fine particles.

(Resin for coating)
Examples of the coating resin include silicone resins, styrene resins, acrylic resins, and styrene acrylic resins. Since the silicone resin has a low surface energy, the carrier core material particles 21 can be coated with the silicone resin to suppress toner component sticking and filming. In order to improve the wear resistance of the carrier coating layer 22, it is preferable to use a cross-linked silicone resin.

  As shown below, the cross-linked silicone resin is a known silicone resin in which hydroxyl groups bonded to Si atoms or a hydroxyl group and an OX group are crosslinked and cured by a heat dehydration reaction, a room temperature curing reaction, or the like.

(In the formula, plural Rs are the same or different and represent a monovalent organic group, and the group OX represents an acetoxy group, an aminoxy group, an alkoxy group, an oxime group, etc.)
As the crosslinkable silicone resin, either a heat curable silicone resin or a room temperature curable silicone resin can be used. In order to crosslink the thermosetting silicone resin, the resin is heated to about 200 to 250 ° C. Moreover, although heating is not required to cure the room temperature curable silicone resin, it may be heated at 150 to 280 ° C. in order to shorten the curing time.

  Among the cross-linked silicone resins, those in which the monovalent organic group represented by R is a methyl group are preferable. This cross-linked silicone resin has a fine cross-linked structure. When the carrier coating layer 22 is formed on the carrier core particles 21 using this cross-linked silicone resin, a coated carrier 20 having good water repellency and moisture resistance can be obtained. However, if the cross-linked structure becomes too dense, the carrier coating layer 22 tends to become brittle, so selection of the molecular weight of the cross-linked silicone resin is important.

  The weight ratio of silicon to carbon (Si / C) in the cross-linked silicone resin is preferably 0.3 to 2.2.

  If Si / C is less than 0.3, the hardness of the carrier coating layer 22 may be reduced, and the carrier life may be reduced. On the other hand, when Si / C exceeds 2.2, the charge imparting property of the carrier to the toner is easily affected by the temperature change, and the carrier coating layer 22 may become brittle.

  Examples of commercially available cross-linked silicone resins include product names manufactured by Toray Dow Corning Co., Ltd .: SR2400, SR2410, SR2411, SR2510, SR2405, 840RESIN, 804RESIN, products manufactured by Shin-Etsu Chemical Co., Ltd .: KR350, KR271, KR272. , KR274, KR216, KR280, KR282, KR261, KR260, KR255, KR266, KR251, KR155, KR152, KR214, KR220, X-4040-171, KR201, KR5202, and KR3093.

(Spherical fine particles)
As the spherical fine particles, polytetrafluoroethylene particles or curable resin fine particles having a volume average particle diameter of 0.2 to 1 μm can be used. Further, the average particle diameter of the spherical fine particles is preferably 2 to 5 times the average particle diameter of the resin fine particles 12 a of the capsule toner 10. Thereby, it can suppress that the resin fine particle 12a is pressed on the surface of the coat carrier 20 by the spacer effect of the microprotrusion 23 formed on the surface of the coat carrier 20.

  The polytetrafluoroethylene fine particles can be produced by emulsion polymerization of a tetrafluoroethylene monomer in an aqueous medium containing a water-soluble polymerization initiator and a surfactant. Examples of commercially available polytetrafluoroethylene fine particles include Lubron L2 (average particle size: 0.3 μm), Lubron L5F (average particle size: 0.4 μm), and Lubron L5 (average particle size: manufactured by Daikin Industries, Ltd.). 0.5 μm) and the like.

  Curable resin fine particles are obtained by emulsion polymerization or soap-free polymerization of methacrylic acid esters such as methyl methacrylate and butyl methacrylate, and monomers such as methyl acrylate, butyl acrylate, and styrene together with cross-linking monomers such as divinylbenzene. Can be manufactured.

<Coat carrier manufacturing method>
As a method of manufacturing the coated carrier 20 provided with the carrier coating layer 22 on the surface of the carrier core material particle 21, for example, an immersion method in which the carrier core material particle 21 is immersed in a resin liquid, a resin liquid is used as the carrier core material particle 21. Spray method, spraying the resin liquid in a state where the carrier core material particles 21 are suspended by the flowing air, mixing the carrier core particle 21 and the resin liquid in a kneader coater, and removing the solvent. Examples include the kneader coater method.

  Among these, the dipping method is preferable in that film formation is easy. In the dipping method, for example, the carrier coating layer 22 is formed by coating the surface of the carrier core material particle 21 with a coating solution in which the constituent material of the carrier coating layer 22 is dissolved or dispersed in a solvent, and then removing the solvent by volatilization. Then, the coated carrier 20 can be manufactured by heat-curing the carrier coating layer 22.

  The solvent is not particularly limited as long as it can dissolve the resin, and examples thereof include aromatic hydrocarbons such as toluene and xylene, ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran and dioxane, and higher alcohols. Such organic solvents are mentioned. A solvent can be used individually by 1 type or in combination of 2 types.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In the following, “part” and “%” mean “part by mass” and “% by mass”, respectively, unless otherwise specified. First, methods for measuring various physical properties will be described.

<Measurement methods for various physical properties>
(Volume average particle size and coefficient of variation of toner base particles)
20 ml of a sample and 1 ml of sodium alkyl ether sulfate are added to 50 ml of an electrolytic solution (trade name: ISOTON-II, manufactured by Beckman Coulter, Inc.), and an ultrasonic dispersion device (trade name: desktop type dual frequency ultrasonic cleaner VS-D100). , Manufactured by ASONE Co., Ltd.) for 3 minutes at a frequency of 20 kHz to obtain a measurement sample. This sample for measurement was measured using a particle size distribution measuring device (trade name: Multisizer 3, manufactured by Beckman Coulter, Inc.) under the conditions of aperture diameter: 100 μm, number of measured particles: 50000 count, and volume particle size distribution of sample particles. Were used to determine the standard deviation in volume average particle size and volume particle size distribution. The coefficient of variation (CV value,%) was calculated based on the following formula.

CV value (%) = (standard deviation in volume particle size distribution / volume average particle size) × 100
(Average particle size and particle size distribution of resin fine particles)
Taking 100 images of resin fine particles magnified 50000 times with a scanning electron microscope (trade name: S-4300SE / N, manufactured by Hitachi High-Technologies Corporation) while changing the field of view, and analyzing the resin fine particles by image analysis The diameter (the length of the line segment obtained by measuring the dimensions in a certain direction and dividing the particle area into two) was measured. A particle size distribution was obtained by calculating a frequency ratio with an arbitrary particle size from the obtained measured value. In this particle size distribution, the particle diameter at which the cumulative number ratio was 50% was defined as the average primary particle diameter of the resin fine particles.

(Volume average particle diameter of resin fine particles)
A measurement sample in which resin fine particles are dispersed (dispersion medium: water (refractive index 1.33), dispersoid: refractive index 1.49) is measured with a laser diffraction scattering method particle size distribution measuring device (Microtrac MT3000, manufactured by Nikkiso Co., Ltd.). ) And measured. And the volume average particle diameter was calculated | required from the volume particle size distribution of the sample for a measurement.

(Glass transition point of resin)
Using a differential scanning calorimeter (trade name: DSC220, manufactured by Seiko Denshi Kogyo Co., Ltd.), according to Japanese Industrial Standard (JIS) K7121-1987, 1 g of a sample was heated at a heating rate of 10 ° C. per minute to obtain a DSC curve. It was measured. In the obtained DSC curve, the slope is maximized with respect to the straight line obtained by extending the base line on the high temperature side to the low temperature side from the endothermic peak corresponding to the glass transition, and the curve from the rising part of the peak to the vertex. The temperature at the intersection with the drawn tangent was defined as the glass transition point (Tg).

(Resin softening temperature)
Using a flow characteristic evaluation apparatus (trade name: Flow Tester CFT-100C, manufactured by Shimadzu Corporation), 1 g of a sample was heated at a heating rate of 6 ° C. per minute, and a load of 20 kgf / cm ² (9.8 × 10 ⁵ Pa). The temperature at which the sample began to flow out of the die (nozzle diameter 1 mm, length 1 mm) was defined as the softening temperature.

(Average particle diameter of carrier)
The particle size distribution was measured using a particle size measuring device (trade name: Microtrac MT3000, manufactured by Nikkiso Co., Ltd.). In this particle size distribution, the value of D50, which is an accumulated particle size up to a volume ratio of 50%, was taken as the average particle size of the carrier.

<Example of capsule toner production>
(Toner mother particles)
100 parts by weight of styrene-butyl acrylate resin (glass transition point 45 ° C., softening temperature 95 ° C.), 10 parts by weight of carbon black (manufactured by Mitsubishi Chemical Corporation, MA-100), and charge control agent (manufactured by Hodogaya Chemical Co., Ltd., TRH) 2 parts by weight and 4 parts by weight of polyethylene wax (Toyo Adre, PW725, melting point 106 ° C.) were mixed and dispersed in a Henschel mixer for 3 minutes, and then twin screw extruder (trade name: PCM-30, Ikekai Co., Ltd.) The mixture was melt kneaded and dispersed.

  The operating conditions of the twin screw extruder were a cylinder set temperature of 110 ° C., a barrel rotation speed of 300 rpm, and a raw material supply speed of 20 kg / hour. The obtained toner kneaded product was cooled with a cooling belt and then coarsely pulverized with a speed mill having a φ2 mm screen. This coarsely pulverized product is finely pulverized with a jet type pulverizer (trade name: IDS-2, manufactured by Nippon Pneumatic Industry Co., Ltd.), and further classified with an elbow jet classifier (product name, manufactured by Nippon Steel Mining Co., Ltd.). As a result, toner base particles 11 having a volume average particle diameter of 6.4 μm and a coefficient of variation of 21 were obtained.

(Resin fine particles)
168 parts by weight of deionized water is charged into a reaction vessel equipped with a stirring and heating device, a thermometer, a nitrogen introducing tube, and a cooling tube, and the temperature is raised to 80 ° C. To this, 252 parts by weight of deionized water, 1 part by weight of polyoxyethylene alkyl ether, 75 parts by weight of styrene and 25 parts by weight of n-butyl acrylate, 1 part by weight of ammonium peroxodisulfate, 0. An initiator aqueous solution composed of 2 parts by weight and 62 parts by weight of deionized water was added dropwise simultaneously over 110 minutes, and the reaction was terminated after stirring for another 60 minutes.

  The obtained latex is dried with hot air using a spray dryer (trade name: Micro Mist Dryer MDL-050, manufactured by Fujisaki Electric Co., Ltd.) and pulverized to have a glass transition point of 60 ° C, a softening temperature of 95 ° C, and a particle size. Of substantially monodispersed resin fine particles 12a having a diameter of 0.1 to 0.3 μm were obtained.

(Capsule toner)
100 parts by weight and 10 parts by weight of toner base particles 11 and resin fine particles 12a are put into a hybridization system (trade name: NHS-1 type, manufactured by Nara Machinery Co., Ltd.) and mixed for 7 minutes at 8000 rpm. Then, the resin fine particles 12a were coated on the surface of the toner base particles 11 to obtain a capsule toner 10 having a volume average particle size of 6.5 μm and a variation coefficient of 23.

  Further, 100 parts by weight of the capsule toner 10 and 0.5 parts by weight of hydrophobic silica fine particles (trade name: KE-P10, manufactured by Nippon Shokubai Co., Ltd.) having an average primary particle size of 100 nm and primary particles 2 parts by weight of hydrophobic silica fine particles having an average particle diameter of 7 nm (trade name: Famed Silica R976, manufactured by Nippon Aerosil Co., Ltd.) are charged into a Henschel mixer (trade name: FM20C, manufactured by Mitsui Mining Co., Ltd.), and the tip of the stirring blade The peripheral speed at the outermost periphery of the part was set to 40 m / second, and the mixture was stirred and mixed for 1 minute, and an external additive composed of hydrophobic silica fine particles was added to the surface of the capsule toner 10.

<Production example of coat carrier>
(Carrier core particles)
Finely pulverized Fe 2 O 3 and MgCO 3 were prepared as raw materials for the carrier core particles 21, weighed so that the molar ratio was Fe 2 O 3: MgCO 3 = 80: 20, and mixed to obtain a metal raw material mixture. An ammonium polycarboxylate-based dispersant equivalent to 1.5 wt% with respect to the total raw material of the carrier core material particles 21, SN wet 980 equivalent to 0.05 wt% (wetting agent, manufactured by San Nopco Corporation); An aqueous solution in which polyvinyl alcohol (binder) corresponding to 02 wt% was added to water was produced to obtain a slurry having a concentration of 75 wt%.

  This slurry was wet pulverized by a wet ball mill and stirred for a while until the volume average particle diameter became 1 μm. The slurry was sprayed with a spray dryer to obtain a dry granulated product having a volume average particle size of 10 to 200 μm. Coarse grains were separated from the granulated product using a sieve net having a mesh size of 61 μm.

  The dried granulated product is calcined by heating at 900 ° C. in the atmosphere, the resin particle component is decomposed to obtain a calcined product, and then the calcined product is calcined for 5 hours in a nitrogen atmosphere at 1160 ° C. To obtain a baked product. The fired product was crushed with a hammer mill, fine powder was removed using an air classifier, and the particle size was adjusted with a vibrating screen having a mesh size of 54 μm to obtain carrier core particles 21 having an average particle size of 35 μm.

(Coat carrier)
Polytetrafluoroethylene fine particles having an average particle size of 0.3 to 0.5 μm (trade name: Lubron, manufactured by Daikin Industries, Ltd.), 0.5 part by weight, and a crosslinked silicone resin (trade name: KR350, Shin-Etsu Chemical Co., Ltd.) 3 parts by weight of company), 15 parts by weight of toluene, 0.1 part by weight of conductive particles (trade name: VULCAN XC-72, manufactured by Cabot Corporation), and coupling agent (trade name: Z-6011, Toray) -0.10 parts by weight of Dow Corning Co., Ltd. and 0.06 parts by weight of a curing catalyst (trade name: Orgatics TC-401, Matsumoto Fine Chemical Co., Ltd.) : Three-one motor BLh1200), and stirred for 5 minutes at 500 rpm to prepare a coating solution.

  100 parts by weight of carrier core material particles 21 having an average particle diameter of 35 μm were mixed with the obtained coating liquid, and further mixed for 5 minutes at a rotation speed of 500 rpm using the above stirrer. The obtained mixture was depressurized (about 6.0 × 10 4 Pa) and heated (about 100 ° C.) to remove the solvent toluene, and a coating layer was formed on the surface of the carrier core material.

  The obtained carrier core material having the coating layer is heated at 200 ° C. for 1 hour using a safety oven (manufactured by ESPEC Corporation, model: SPH (H) 102) to cure the coating layer to form a resin layer. The coated carrier 20 was obtained through a 100-mesh sieve.

  The obtained capsule toner 10 and coat carrier 20 were mixed for 20 minutes with a V-type mixer (trade name: V-5, manufactured by Tokuju Kogakusho Co., Ltd.) so that the toner concentration would be 7%. The two-component developer 1 shown in Fig. 1 was prepared, and the stability of the charging stability was evaluated.

Example 1
As a two-component developer, a capsule toner in which a coating layer is formed with resin fine particles of a styrene-butyl acrylate copolymer having an average particle size of 0.1 μm, and polytetrafluoroethylene particles having an average particle size of 0.3 μm are coated. A coat carrier on which a layer was formed was used.

(Example 2)
Instead of the capsule toner of Example 1, a capsule toner having a coating layer formed of resin fine particles of a styrene-butyl acrylate copolymer having an average particle size of 0.15 μm was used.

(Example 3)
Instead of the capsule toner of Example 1, a capsule toner having a coating layer formed of resin fine particles of a styrene-butyl acrylate copolymer having an average particle diameter of 0.3 μm was used.

(Examples 4 to 6)
Instead of the coated carriers of Examples 1 to 3, a coated carrier having a coating layer formed of polytetrafluoroethylene particles having an average particle diameter of 0.4 μm was used.

(Examples 7 to 9)
Instead of the coated carriers of Examples 1 to 3, a coated carrier having a coating layer formed of polytetrafluoroethylene particles having an average particle diameter of 0.5 μm was used.

(Comparative Examples 1-3)
Instead of the coated carriers of Examples 1 to 3, a coated carrier having a coating layer containing no spherical fine particles was used.

<Evaluation method>
(Charge stability)
A two-component developer is set in a copying machine (trade name: MX-5000FN, color print speed 50 ppm, monochrome print speed 50 ppm, manufactured by Sharp Corporation), and an image with a printing rate of 25% is 50,000 (50K) at room temperature and humidity. A sheet was printed. The charge stability of the two-component developer was evaluated using the charge amount of the two-component developer before and after printing 50K sheets. The initial charge of the two-component developer (before printing 50K sheets) and the charge amount after printing 50K sheets are obtained by sucking toner through a mesh using a suction type small charge amount measuring device (trade name: 210HS-2A, manufactured by TREK Co., Ltd.). Then, the charge of the separated toner was measured, the charge amount [-μc / g] was calculated from the measured charge and the weight of the separated toner, and the charging stability was evaluated according to the following criteria.
A: The difference between the initial charge amount and the charge amount after printing 50K sheets is less than 3 μC / g.
A: The difference between the initial charge amount and the charge amount after printing 50K sheets is 3 μC / g or more and 4 μC / g or less.
Δ: The difference between the initial charge amount and the charge amount after printing 50K sheets is 4 μC / g or more and 5 μC / g or less.
X: The value obtained by subtracting the charge amount after 50K printing from the initial charge amount is larger than 5 μC / g.

  In the two-component developer 1 of the present invention shown in Examples 1 to 9, the difference between the initial charge amount and the charge amount after printing 50K sheets is as small as 3 to 5 μC / g. Stability could be maintained.

  In the conventional two-component developers of Comparative Examples 1 to 3, the difference in the initial charge amount and the charge amount after printing 50K sheets is as large as 5 μC / g or more, and the charging performance is deteriorated. The sex could not be maintained.

  In the two-component developer 1 of the present invention, the carrier coating layer includes spherical fine particles, and the fine particles 23 are formed on the surface of the coated carrier 20 by the spherical fine particles as shown in FIG. For this reason, when the two-component developer 1 is agitated in the developing device, the two coat carriers 20 that are close to each other engage with each other to rotate with the microprotrusions 23 therebetween. It is considered that the resin fine particles 12a function to discharge to the outside and prevent the resin fine particles 12a from being fused to the surface of the coat carrier 20.

  On the other hand, in the conventional two-component developer, as shown in FIG. 2, since the microcarriers are not provided on the surface of the coat carrier 60, the coat carriers 20 close to each other are in the same direction (for example, clockwise in FIG. 2). There may be rotational movement. At this time, the resin fine particles 12a are rubbed against the surface of the coat carrier 20 to generate frictional heat, and fusion to the surface of the coat carrier 20 occurs. For this reason, the coated carrier 20 covered with the resin fine particles 12a is considered to have a small potential difference from the capsule toner 10 and to decrease the charging stability.

DESCRIPTION OF SYMBOLS 1 Two-component developer 10 Capsule toner 11 Toner mother particle 12 Toner coating layer 12a Resin fine particle 20 Coat carrier 21 Carrier core particle 22 Carrier coating layer 23 Microprotrusion

Claims (5)

A two-component developer comprising a capsule toner having resin fine particles formed on the surface of toner base particles and a coated carrier having a carrier coating layer formed on the surface of carrier core particles,
A two-component developer, wherein fine protrusions are formed on the carrier coating layer.   The two-component developer according to claim 1, wherein the fine protrusions are formed of spherical fine particles.   The two-component developer according to claim 2, wherein the spherical fine particles have an average particle diameter of 2 to 5 times the average particle diameter of the resin fine particles.   The two-component developer according to claim 3, wherein the spherical fine particles are polytetrafluoroethylene particles.   The two-component developer according to any one of claims 1 to 4, wherein the carrier coating layer contains a silicone resin.